PHILADELPHIA (AP) — Legal experts raised alarm when U.S. court officials confirmed that their electronic case files had been compromised as part of a sweeping attack on U.S. computer networks. Russian hackers seemingly gained access to a vast trove of private information hidden in sealed files, and that could include trade secrets, espionage targets, whistleblower reports and arrest warrants. Trial lawyers are now preparing to hand-deliver hard copies of highly sensitive documents to the courts instead of uploading them online. Some people worry that the new rules will reduce public access to court proceedings, but the rules could also make judges rethink whether a seal or paper filing is really necessary.